In a 2 quart saucepan, heat 3 cups of strawberries over medium heat.
Bring the strawberry mixture to a boil and then continue simmering, stirring frequently, until nearly all liquid has evaporated.
Use a potato masher to break down strawberries as they cook, if you’ve added strawberry pieces. This process takes approximately 20 minutes, and the 3 cups of strawberries should reduce to about 3/4 cup.
Remove puree reduction from heat and cool to room temperature in the refrigerator before adding to cake batter, approximately 1 hour.
Preheat the oven to 350°F (325°F for dark/non-stick pans).
Line the bottom of two 8-inch cake pans with parchment paper and spray the sides with non-stick cooking spray. Set aside.
In a mixing bowl combine cake mix, strawberry gelatin, eggs, water, and oil.
Mix in 1/2 cup of the cooled strawberry puree reduction until combined.
Divide batter between the two prepared cake pans.
Bake for 25 to 30 minutes or until a toothpick inserted in the center of the cake comes out clean.
Remove pans and cool for 10 minutes. Gently remove cakes from pans to cooling racks and cool completely.
Beat together softened cream cheese, butter, and strawberry extract until combined.
Beat in 5 cups of powdered sugar.
Beat in remaining 1/4 cup of strawberry puree reduction.
Add 1 tablespoon of heavy cream at a time until desired consistency of frosting is achieved.
Add pink food coloring to tint frosting to the desired color.
Trim the top of each cake layer to remove any doming and form a flat surface.
Place the first cake layer top-side up onto the serving platter.
Mound about 1/2 cup of frosting onto the cake layer and spread smooth to the edges.
Place the second cake layer top-side down on top of the filling. Press down gently to seal the layers together.
Mound another pile of frosting on top of the cake and use a spatula to spread it across the top and down the sides until the cake is fully frosted.
Refrigerate or freeze until ready to serve.